THE SOIL AS AN ASSET 219 



ever, this doleful prediction has been swept 

 aside as untenable by accepted theories. The 

 air we breathe is four-fifths nitrogen, and 

 Hellriegel in 1886 was able to isolate a bac- 

 terium from the roots of clover, whose func- 

 tion is to extract nitrogen from the air and 

 make it available for plants. It is estimated 

 that upward of 35,000 tons of nitrogen hangs 

 suspended over every acre, and, were there no 

 other means of putting it in the soil than the 

 bacteria of legumes, there need be no fear that 

 any farm acre, under proper systems of culti- 

 vation and rotation, will ever be deficient in 

 this element. 



There are other means of extracting nitro- 

 gen from the air. There are other flora and 

 fauna of the soil which make it their main task 

 to extract it from the air and manufacture it 

 in the form of nitrates. Mr. A. D. Hall of 

 the Rothamsted station, the most famous ex- 

 periment station in the world, tells (Chemical 

 News, Vol. 106) how a soil that was permitted 

 to run wild for 23 years was found to have 

 gained 92 pounds of nitrogen per acre each 

 year. As nitrogen as a commercial fertilizer 

 is worth upward of 18 cents a pound, the im- 

 portance of this fact can be seen. In this 



